Mask for manufacturing semiconductor device and method of manufacture thereof

ABSTRACT

The present invention relates to a microminiaturization technique to achieve the miniaturization and higher integration of IC chip and to the improvement of a mask used in its manufacturing process. In other words, the phases of lights transmitted through the mask is controlled within one mask pattern. Specifically, a transparent film is formed in such a manner that it covers a mask pattern along a pattern formed by magnifying or demagnifying the mask pattern or otherwise a groove is formed in a mask substrate. A phase difference of 180° is generated between the lights transmitted through the mask substrate and the transparent film or the groove, causing interference with each light to offset each other. Therefore, the pattern transferred onto a wafer has an improved resolution, being used in the invention.

This is a Continuation application of application Ser. No. 09/580,424,filed May 30, 2000, which is a Continuation application of applicationSer. No. 09/287,561, filed Apr. 6, 1999, which is a Continuationapplication of application Ser. No. 09/099,332, filed Jun. 18, 1998,which is a Continuation application of application Ser. No. 08/829,233,filed Mar. 31, 1997, now U.S. Pat. No. 5,830,606, which is aContinuation application of application Ser. No. 08/631,000, filed Apr.12, 1996, now U.S. Pat. No. 5,643,698, which is a Continuationapplication of application Ser. No. 08/449,926, filed May 25, 1995, nowU.S. Pat. No. 5,631,108, which is a Divisional application ofapplication Ser. No. 08/288,905, filed Aug. 11, 1994, now U.S. Pat. No.5,484,671, which is a Divisional application of application Ser. No.08/087,074, filed Jul. 7, 1993, now U.S. Pat. No. 5,358,807, which is aContinuation application of application Ser. No. 07/730,221, filed Jul.15, 1991, now abandoned, which is a Continuation application ofapplication Ser. No. 07/437,268, filed Nov. 16, 1989, now U.S. Pat. No.5,045,417 and is a Continuing application of application Ser. No.08/051,552, filed Apr. 23, 1993, now U.S. Pat. No. 5,306,585,application Ser. No. 08/051,351, filed Apr. 23, 1993, now U.S. Pat. No.5,350,649, and application Ser. No. 08/051,238, filed Apr. 23, 1993, nowU.S. Pat. No. 5,352,550.

BACKGROUND OF THE INVENTION

The present invention relates to a mask for use in photolithography andits manufacturing technique, and particularly to a technique effectivelyapplicable to a mask for use of manufacturing semiconductor integratedcircuit device.

In recent years, very fine elements constituting a circuit, very finewirings and very narrow spaces between the elements and wirings havebeen developed in semiconductor integrated circuit devices.

However, along with such development of the elements and wirings and ofthe spaces between elements and wirings, there arises a problem in thatthe accuracy of mask pattern transfer is lowered when an integratedcircuit pattern is transferred onto a wafer by coherent light.

This problem will subsequently be described with reference to FIGS.24(a)-(d).

When a given integrated circuit pattern formed on a mask 50 shown inFIG. 24(a) is transferred onto a wafer by a method of projectionexposure or the like, the phases of lights each transmitted through eachof a pair of transmission regions P₁, P₂ having light shield region Ntherebetween are identical to each other as shown in FIG. 24(b).Consequently, these interferential lights increase their intensities inlight shield region N located between the above-mentioned pair oftransmission regions P₁, P₂ as shown in FIG. 24(c). As a result, asshown in FIG. 24(d) the contrast of a projected image on a wafer is notonly lowered, but also the depth of focus becomes shallow, causing thetransfer accuracy of the mask pattern to be considerably lowered.

As a means to counteract these problems, a technique of phase shiftinglithography has been developed, whereby the phase of light transmittedthrough the mask is controlled so as to improve the resolution andcontrast of the projected image. The phase shifting lithographytechnique is disclosed, for example, in Japanese Laid-Open Patent No.173744/1983 and Japanese Laid-Open Patent No. 67514/1987.

In the above-mentioned Japanese Laid-Open Patent No. 173744/1983 thereis described the structure of a mask having a light shield region and apair of transmission regions, wherein a transparent material is arrangedat least in either one of the transmission regions sandwiching the lightshield region therebetween, allowing a phase difference to be generatedbetween the lights each transmitted through each of transmission regionsat the time of exposure and thus these lights being interfered with eachother to weaken themselves in the region on a wafer which shouldprimarily be a light shield region.

The function of the light transmitted through such a mask as above willsubsequently be described with reference to FIGS. 25(a)-(d).

When a given integrated circuit pattern formed on a mask 51 shown inFIG. 25(a) is transferred onto a wafer by the method of projectionexposure or the like, a phase difference of 180° is generated betweenthe phase of light transmitted through a transmission region P₂ havingtransparent material 52 of a pair of transmission regions P₁, P₂ whichhave light shield region N sandwiched therebetween and the phase oflight transmitted through the normal transmission region P₁ as shown inFIGS. 25(b) and (c). Therefore, the lights transmitted through the pairof transmission regions P₁, P₂ interfere with each other to offset themin light shield region N located between these transmission regions P₁,P₂. Consequently, as shown in FIG. 25(d), the contrast of a projectedimage on a wafer is improved. Thus, the resolution and depth of focus isimproved, resulting in a higher accuracy of pattern transfer of the mask51.

Also, in the above-mentioned Japanese Laid-Open Patent No. 67514/1987,there is described the structure of a mask having a light shield regionformed by light shielding film and a transmission region formed byremoving the light shielding film, wherein a fine aperture pattern isformed by removing a part of shielding film and at the same time, aphase shifting layer is provided on either one of the transmissionregion or the aperture pattern, and thus a phase difference is generatedbetween the lights transmitted through the transmission region and theaperture pattern, preventing the distribution of amplitude of lighttransmitted through the transmission region from being spread in thehorizontal direction.

SUMMARY OF THE INVENTION

Nevertheless, the present inventor has found that the conventionaltechnique disclosed in the above-mentioned Japanese Laid-Open Patent No.173744/1983 has the following problem:

The above-mentioned conventional technique in which a phase differenceis generated between the lights transmitted through the pair oftransmission regions does not has any problem as far as a pattern issimply and unidimensionally arranged in a repetitive manner. However, inthe case that the pattern is complicated as in an actual integratedcircuit pattern, the arrangement of the transparent material may beimpossible, and a problem arises in that sufficient resolution is notobtained at some sections.

For example, in the case of an integrated circuit pattern 53 shown inFIG. 26. If transparent material is arranged in a transmission regionP₂, the resolutions in light shield regions N₁ and N₂ are certainlyimproved. However, if transparent material is arranged in transmissionregion P₁ in order to improve the resolution in light shield region N₃,the lights transmitted through transmission regions P₁, P₂ will have anidentical phase, causing the resolution in light shield region N₂ to belowered. Also, in order to improve the resolution in the light shieldregion N₃, a transparent material should be provided in such atransmission region as the transmission region P₃. Then, the transparentmaterial can be arranged in a part of transmission region P₃. In such acase, however, there appears the reversing of phases in the lightstransmitted through the same transmission region P₃, and an unwantedpattern is formed on a wafer. Consequently, it becomes impossible toimprove the resolution in light shield region N₃.

Furthermore, if the pattern is complicated like an actual integratedcircuit one, the arrangement of transparent material is restricted asmentioned above. This makes it difficult to prepare the pattern data ofthe transparent material. Conventionally, therefore, the pattern of thetransparent material should be produced specially while taking intoconsideration the above-mentioned restriction on the arrangement when amask having means for shifting phase of light is manufactured.

On the other hand, the known technique disclosed in Japanese Laid-OpenPatent No. 67514/1987, whereby an aperture pattern is formed in a lightshield region so as to generate a phase contrast between the lighttransmitted through the aperture pattern and the one transmitted throughthe transmission region, makes it difficult to arrange the aperturepattern, the same as in the case of the above-mentioned publication, ifa pattern is as complicated and extremely fine as an actual integratedcircuit pattern. For example, should the width of pattern of lightshield region become narrower, there arises a problem in that thearrangement of an aperture pattern is difficult.

Furthermore, in this conventional technique, no consideration is givenas to the lowering of light intensity at the corners of transmissionregion which takes place along with a further miniaturization oftransmission region required, resulting in a problem posed in that thecorners of a projected image are rounded.

The present invention is to solve the above-mentioned problems, and theobject thereof is to provide a technique whereby the transfer accuracyof a pattern formed on a mask can be improved.

Another object of the present invention is to provide a techniquewhereby the manufacturing time of a mask having means for shifting phaseof light can be reduced.

Still another object of the present invention is to provide a techniquewhereby the resolution of not only each side of a projected image butalso of each corner thereof can be improved.

Among the inventions to be disclosed in the present application, thosetypical ones will subsequently be described.

Now, the first invention is a mask having light shield and transmissionregions and transferring a given pattern at least by irradiation ofcoherent light locally, wherein a phase shifting portion is formed in apart of the aforementioned transmission region for shifting a phase oflight transmitted, and a phase contrast is generated between the lighttransmitted through the aforementioned phase shifting portion and thelight transmitted through the transmission region where theaforementioned phase shifting portion is not formed, and theaforementioned phase shifting portion is so arranged that theinterferential lights of the aforementioned lights can weaken themselvesin the boundary area of the aforementioned transmission and light shieldregions.

The second invention is the method of manufacturing a mask wherein thepattern data of the phase shifting portion can automatically be preparedin accordance with the pattern data of the light shield region.

The third invention is a mask in which light shield and transmissionregions are provided on a mask substrate and a given pattern in the maskis transferred at least by the irradiation of coherent light locally,wherein a groove having a depth to reach the main surface of theaforementioned mask substrate is formed, and simultaneously a phasecontrast is generated between the light transmitted through theaforementioned groove and the light transmitted through theaforementioned transmission region, and a phase shifting groove isformed on the aforementioned mask substrate located below theaforementioned groove so as to allow the interferential lights of theaforementioned lights to weaken themselves at the end portion of theaforementioned light shield region.

The fourth invention is a mask in which light shield and transmissionregions are provided on a mask substrate, and a given pattern istransferred at least by the irradiation of coherent light locally,wherein a groove having a depth to reach the main surface of theaforementioned mask substrate is formed in a part of the aforementionedlight shield region, and a phase contrast is generated between the lighttransmitted through the aforementioned groove and the light transmittedthrough the aforementioned transmission region, and a transparent filmis provided above the aforementioned groove so as to allow theinterferential lights of the aforementioned lights to weaken themselvesat the end portion of the aforementioned light shield region, andsimultaneously, subtransmission regions are formed at the corners of theaforementioned transmission region.

According to the first invention mentioned above, the light transmittedthrough the phase shifting portion and the light transmitted through theportion where it is not formed interfere with each other to weakenthemselves at the boundary portion of transmission and light shieldregions so that the bleeding of contour of an image projected on a wafercan be reduced, and the contrast of the projected image can be improvedconsiderably, resulting in a remarkable improvement of the resolutionand death of focus.

Particularly, in the present invention, no restriction on thearrangement of phase shifting portion takes place no matter howcomplicated the pattern is on the mask. Also, there is no difficulty inarranging the phase shifting portion no matter how narrow the width ofpattern becomes in the light shield region.

According to the second invention mentioned above, the manufacturingtime of a mask having means for shifting phase of the light can bereduced considerably because there is no need for preparing speciallyany pattern data of transparent film or phase shifting groove.

According to the third invention mentioned above, the light transmittedthrough the groove and phase shifting groove interfere with each otherto weaken themselves, making it possible to reduce the bleeding ofcontour of a projected image and to improve the contrast thereof so thatthe solution and depth of focus can be improved remarkably.

According to the fourth invention mentioned above, the light intensityat the corner of a transmission region increases by the arrangement of asub-transmission region thereat so that not only the resolution at eachside of a projected image, but also the resolution at the cornerthereof, can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of the principal part of a mask embodying thepresent invention,

FIGS. 2(a)-(c) are sectional views illustrating the principal part ofthe mask in the respective processes of the manufacture thereof,

FIG. 3(a) is a sectional view of the mask shown in FIG. 1 in a state ofexposure,

FIGS. 3(b)-(d) are diagrams representing the amplitude and intensity ofthe light being transmitted through the transmission region of the mask,

FIG. 4 is a sectional view of the principal part of another maskembodying the present invention,

FIG. 5(a) is a sectional view of the mask shown in FIG. 4 in a state ofexposure,

FIGS. 5(b)-(d) are diagrams representing the amplitude and intensity ofthe light being transmitted through the transmission region of the maskshown in FIG. 4,

FIG. 6 is a sectional view of the principal part of another maskembodying the present invention,

FIG. 7 shows top plan views of the principal part of the mask shown inFIG. 6,

FIG. 8 illustrates the construction of a focused ion beam systememployed in the manufacture of the mask,

FIGS. 9(a) and (b) are sectional views illustrating the principal partof the mask in the respective processes of the manufacture thereof,

FIG. 10 is a flow chart representing the procedures through which thepattern data for a phase shifting groove are prepared,

FIG. 11(a) is a sectional view of the mask shown in FIG. 6 in a state ofexposure,

FIGS. 11(b)-(d) are diagrams representing the amplitude and intensity ofthe light being transmitted through the transmission region of the maskshown in FIG. 6,

FIG. 12 is a sectional view of the principal part of another maskembodying the present invention,

FIG. 13(a) is a sectional view of the mask shown in FIG. 12 in a stateof exposure,

FIGS. 13(b)-(d) are diagrams representing the amplitude and intensity ofthe light being transmitted through the transmission region of the maskshown in FIG. 12,

FIG. 14 is a sectional view of the principal part of still another maskembodying the present invention;

FIG. 15 is a top plan view of the principal part of the mask shown inFIG. 14,

FIG. 16 is a top plan view of the principal part of a mask showing anexample of pattern data for a groove and a sub-transmission region.

FIG. 17 is a flow chart representing the procedures through which thepattern data for the groove and sub-transmission region shown in FIG. 16are prepared,

FIGS. 18(a)-(i) are illustrations showing the shapes of the pattern inthe course of forming the pattern for the groove and sub-transmissionregion shown in FIG. 16,

FIG. 19(a) is a sectional view of the mask shown in FIGS. 14 and 15 in astate of exposure,

FIGS. 19(b)-(d) are diagrams representing the amplitude and intensity ofthe light being transmitted through the transmission region of the maskshown in FIGS. 14 and 15,

FIG. 20 is a sectional view of the principal part of still another maskembodying the present invention,

FIG. 21 is a top plan view of the principal part of the mask,

FIG. 22(a) is a sectional view of the mask shown in FIGS. 20 and 21 in astate of exposure,

FIGS. 22(b)-(d) are diagrams representing the amplitude and intensity ofthe light being transmitted through the transmission region,

FIG. 23 is a sectional view of the principal part of still another maskembodying the present invention,

FIG. 24(a) is a sectional view of a conventional mask in a state ofexposure,

FIGS. 24(b)-(d) are diagrams representing the amplitude and intensity ofthe light being transmitted through the transmission region of theconventional mask,

FIG. 25(a) is a sectional view of a conventional mask in a state ofexposure,

FIGS. 25(b)-(d) are diagrams representing the amplitude and intensity ofthe light being transmitted through the transmission region of theconventional mask,

FIG. 26 is a partial top plan view illustrating part of the conventionalmask.

DESCRIPTION OF A PREFERRED EMBODIMENT Embodiment 1

FIG. 1 is a sectional view of the principal part of a mask embodying thepresent invention, and FIGS. 2(a)-(c) are sectional views illustratingthe principal part of the mask in the respective processes of themanufacture thereof, FIG. 3(a) is a sectional view of the mask shown inFIG. 1 in a state of exposure, and FIGS. 3(b)-(d) are diagramsrepresenting the amplitude and intensity of the light being transmittedthrough the transmission region of the mask.

Mask 1 a shown in FIG. 1 of Embodiment 1 is, for example, a reticle usedat a given process in manufacturing a semiconductor integrated circuitdevice. Also, the original pattern of integrated circuit, which is, forexample, five times its actual dimensions, is formed on the mask 1 a ofEmbodiment 1.

Transparent mask substrate (hereinafter referred to simply as substrate)2 constituting mask 1 a is made of synthetic quartz glass or the likehaving, for example, a refractive index of 1.47. On the main surface ofsubstrate 2, metal layer 3 of, for example, 500-3,000 Å thick ispatterned in a given shape.

Metal layer 3 comprises, for example, a Cr film so that it willconstitute a light shield region A at the time of exposure. Also, metallayer 3 may be of a laminating construction having chromium oxidelaminated on the upper surface of a Cr layer.

Furthermore, the portion where the metal layer has been removedconstitutes a transmission region B, and the original pattern of theintegrated circuit formed on mask 1 a comprises of the light shieldregion A and the transmission region B.

In mask 1 a of Embodiment 1, transparent film 4 a formed in a patternslightly wider than that of the above-mentioned pattern of metal layer 3is provided on mask 1 a in such a manner that its part extends over thecontour of metal layer 3 into the transmission region B. Consequently,one transmission region B comprises of the region which is covered bytransparent film 4 a and the region which is not covered thereby.

Transparent film 4 a is formed, for example, with indium oxide (InOx). Amaterial having a sufficiently high transmittance against substrate 2(at least more than 90% required) as well as an excellent property ofadhesiveness to substrate 2 should be selected as a material fortransparent film 4 a. The width of the excessive portion of transparentfilm 4 a is approximately 0.5 μm, provided that, for example, the widthof pattern of transmission region B is approximately 2 μm. Given thethickness of transparent film 4 a measured from the main surface ofsubstrate 2 is X₁, the refractive index of transparent film 4 a is n₁,and the wavelength of light irradiated at the time of exposure is λ,transparent film 4 a is formed to satisfy the relation ofX₁=λ/[2(n₁−1)]. This relation is maintained in order to generate a phasecontrast of 180° at the time of exposure between the light transmittedthrough transparent film 4 a and the one through the normal transmissionregion B in one transmission region B. For example, if the wavelength λof light irradiated at the time of exposure is 0.365 μm (i line) and therefractive index n₁ of transparent film 4 a is 1.5, the thickness of X₁transparent film 4 a measured from the main surface of substrate 2 willbe approximately 0.37 μm. Although not shown in the drawing, analignment mark is provided on mask 1 a to align its position with thatof metal layer 3 when, for example, transparent film 4 a is formed.

Next, the method of manufacturing mask 1 a of Embodiment 1 will bedescribed with reference to FIGS. 2(a)-(c).

First, the surface of transparent substrate 2 made of synthetic quartzglass or the like is ground, and after it is cleaned, metal layer 3 madeof Cr or the like of, for example, approximately 500-3,000 Å is formedon its main surface by sputtering or others as shown in FIG. 2(a).Subsequently, on the metal layer 3, photoresist (hereinafter referred toas resist) Sa of, for example, 0.4-0.8 μm will be coated. Then, afterresist 5 a is prebaked, a given portion of 5 a is irradiated withelectron beam E by the electron beam exposure method or the like inaccordance with the integrated circuit pattern data with the integratedpattern data of a semiconductor integrated circuit device coded andstored in advance in a magnetic tape which is not shown in the drawing.In the integrated circuit pattern data, the position coordinate, shapeor others are also stored.

Next, as shown in FIG. 2(b), the exposed portion of resist 5 a, forexample, is removed by a developing solution. Then, the exposed metallayer 3 is removed by etching with a dry etching method or the like togain the pattern of a given shape.

Subsequently, resist 5 a is removed by an exfoliative agent andsubstrate 2 is cleaned. Then, after inspection, as shown in FIG. 2(c),the main surface of substrate 2 is covered with transparent film 4 a ofindium oxide (InO_(x)) or others by a sputtering method or the like. Atthis juncture, the thickness X₁ of the transparent film measured fromthe main surface of substrate 2 is, for example, approximately 0.37 μm.

After that, the upper surface of transparent film 4 a is coated withresist 5 b of, for example, 0.4-0.8 μm and furthermore, on its uppersurface, an aluminum antistatic layer 6 of, for example, 0.05 μm thickis formed by a sputtering method or the like. Subsequently, the patternformed on transparent film 4 a will be transferred to resist 5 b by anelectron beam exposure system or the like in accordance with the patterndata of transparent film 4 a.

The pattern data of transparent film 4 a is automatically formed bymagnifying or demagnifying the light shield region A or transmissionregion B of the above-mentioned pattern data of the integrated circuit.In embodiment 1, for example, the pattern data of transparent film 4 ais automatically formed by thickening the pattern width of light shieldregion A by, for example, approximately 0.5-2.0 μm.

Then, mask 1 a shown in FIG. 1 will be produced through the processes ofdevelopment, etching of a predetermined portion of transparent film 4 a,removal of resist 5 b, cleaning, inspection and others.

In order to transfer the pattern of the integrated circuit formed onmask 1 a onto a wafer covered with resist by use of the mask 1 a thusproduced, the following steps will be taken, for example.

Mask 1 a and a wafer are set on a projection aligner for demagnification(which is not shown in the drawing), whereby the original pattern ofintegrated circuit on mask 1 a is projected on a wafer after it has beenreduced to ⅕ optically, and each time the wafer is sequentially movedstep by step, rejection and exposure are repeated so that the pattern ofthe integrated circuit formed on mask 1 a can be transferred onto theentire surface of the wafer.

Next, the function of Embodiment 1 will be described with reference toFIGS. 3(a)-(d).

In mask 1 a of Embodiment 1 shown in FIG. 3(a), a phase contrast of 180°is generated between the light transmitted through transparent film 4 aand the one through the normal transmission region B (FIGS. 3(b) and(c)) in each of transmission regions B of mask 1 a when the originalpattern of a given integrated circuit formed on mask 1 a is transferredonto a wafer by a projection aligner for demagnification or others.

Here, the lights transmitted through the same transmission region Bhaving reverse phases respectively weaken each other at the boundaryarea of transmission region A and light film 4 a is shield region 3because transparent film 4 a is arranged around transmission region B.As a result, the bleeding of a contour of image projected on the waferis reduced so as to improve the contrast of the projected imageconsiderably. Thus, the resolution and depth of focus will remarkably beimproved (FIG. 3(d)). Also, since light intensity is the square of lightamplitude, the waveform in a negative side is reversed to a positiveside as shown in FIG. 3(d).

In this way, it is possible to attain the following effect according toEmbodiment 1:

(1). While lights are being transmitted through each of the transmissionregions B at the time of exposure, a phase contrast of 180° is generatedbetween the light transmitted through transparent film 4 a and the onethrough the region which is not covered with transparent film 4 a. Theselights thus transmitted weaken each other at the boundary area of lightshield region A and transmission region B, making it possible to reducethe bleeding of contour of image projected on the wafer. As a result,the contrast of the projected image is considerably improved so that theresolution and depth of focus can be improved remarkably.

(2). Through (1) mentioned above, more tolerance for exposure can beallowed.

(3). Since a phase contrast can be generated within one transmissionregion B, the arrangement of transparent film 4 a is not restricted nomatter how complicated the pattern is on mask 1 a. Also, the arrangementof transparent film 4 a can be made with ease no matter how narrow thepattern width is in light shield region A. Consequently, the patterntransfer accuracy will never be lowered locally even when a patternformed on mask 1 a is highly complicated and fine like the pattern of anintegrated circuit so that the pattern transfer accuracy of the entirepattern formed on mask 1 a can be improved remarkably.

(4). The pattern data of transparent film 4 a can be obtainedautomatically based on the pattern data of light shield region A ortransmission region B, making it possible to prepare the pattern data oftransparent film 4 a in a short period of time and also with ease. As aresult, a remarkable reduction in time required for the manufacture of aphase shifting mask can be achieved.

Embodiment 2

FIG. 4 is a sectional view of the principal part of another maskembodying the present invention, FIG. 5(a) is a sectional view of themask shown in FIG. 4 in a state of exposure, and FIGS. 5(b)-(d) arediagrams representing the amplitude and intensity of the light beingtransmitted through the transmission region of the mask in FIG. 4.

In mask 1 b of Embodiment 2 shown in FIG. 4, transparent film 4 b isarranged in the vicinity of the central part of transmission region B.

In this case, too, transparent film 4 b is formed on substrate 2 in sucha manner that its thickness X₁ will satisfy the relation ofX₁=λ/[2(n₁−1)] so as to generate as shown in FIGS. 5(b)-(d) the phasecontrast of 180° between the light transmitted through transparent film4 b and the one through the normal transmission region B in each oftransmission regions B, B of mask 1 b (FIGS. 5(b) and (c)). These lightsthus transmitted will weaken each other at the boundary area oftransmission region B and adjacent light shield regions A, A so that thebleeding of contour of the image projected on a wafer can be reduced. Asa result, the contrast of a projected image can be considerablyimproved, making it possible to improve the resolution and depth offocus remarkably (FIG. 5(d)).

Also, in this case, the pattern data of transparent film 4 b canautomatically be prepared by thinning by a given dimension the width ofa pattern of transmission region B which has been obtained by reversingthe positive pattern data of, for example, an integrated circuit patternto the negative one.

According to Embodiment 2, therefore, the same effects as in theaforementioned Embodiment 1 can be attained.

Embodiment 3

FIG. 6 is a sectional view of the principal part of another maskembodying the present invention, FIG. 7 shows top plan views of theprincipal part of the mask shown in FIG. 6, FIG. 8 illustrates theconstruction of a focused ion beam system, FIGS. 9(a) and (b) aresectional views illustrating the principal part of the mask in therespective processes of the manufacture thereof, FIG. 10 is a flow chartrepresenting the procedures through which the pattern data for a phaseshifting groove are obtainable, FIG. 11(a) is a sectional view of themask shown in FIG. 6 in a state of exposure, and FIGS. 11(b)-(d) arediagrams representing the amplitude and intensity of the light beingtransmitted through the transmission region of the mask shown in FIG. 6.

The mask of Embodiment 3 will subsequently be described with referenceto FIGS. 6 and 7. The crosshatching in FIG. 7 shows the light shieldregion A.

In mask 1 c of Embodiment 3, phase shifting groove 7 a is formed onsubstrate 2 instead of transparent film 4 a of aforementioned Embodiment1 as a means for generating a phase contrast between the lights beingtransmitted through transmission region B at the time of exposure.

Phase shifting groove 7 a is arranged around transmission region B. Inother words, phase shifting groove 7 a is arranged along the contour ofmetal layer 3. The width of phase shifting groove 7 a is approximately0.5 μm if the pattern width of transmission region B is given to be, forexample, approximately 2.0 μm. Then, phase shifting groove 7 a is formedto satisfy the relation of d=λ/[2(n₂−1)] where d is the depth thereof,n₂ is the refractive index of substrate 2, and λ is the wavelength oflight irradiated at the time of exposure. This relation is maintained togenerate a phase contrast of 180° between the phase of light transmittedthrough phase shifting groove 7 a and that of light through the normaltransmission region B in the lights being transmitted through each oftransmission regions B at the time of exposure. For example, in casewhere the wavelength λ of the light irradiated at the time of exposureis given to be 0.365 μm (i line), the depth d of phase shifting groove 7a can be approximately 0.39 μm. Also, although not shown in the drawing,an alignment mark is provided on mask 1 c when, for example, phaseshifting groove 7 a is formed to align its position with that of metallayer 3.

Next, a focused ion beam system 8 for use in manufacturing mask 1 c willbe described with 25, reference to FIG. 3.

Inside ion source 9 installed above the system body, such a dissolvedliquid metal as gallium (Ga) or the like, for example, is contained,though not shown in the drawing. Below ion source 9, withdrawableelectrode 10 is installed, beneath which is provided the first lenselectrode 11 a and the first aperture electrode 12 a formed by staticlens. Below aperture electrode 12 a, the second lens electrode 11 b, thesecond aperture electrode 12 b, blanking electrodes 13 for controllingthe on/off of beam irradiation, and then third aperture electrode 12 cand deflection electrode 14 are installed.

With the formation of each electrode thus installed, the ion beamemitted from ion source 9 is irradiated under the controls of theabove-mentioned blanking electrodes 13 and deflection electrode 14 ontothe mask 1 c which is held by holder 15 with patterns yet to be formedthereon. Then, metal layer 3 or substrate 2 can be processed by etchingwith the ion beam by setting at the time of scanning beforehand itsirradiation time and scanning numbers per unit of pixel of, for example,0.02×0.02 μm.

Holder 15 is installed on the sample stand 16 movable in the directionsof X and Y, and sample stand 16 can be positioned by sample standdriving motor 19 when its position is recognized by laser interferometer18 through laser mirror 17 installed at the side of the sample stand.Also, above holder 15, there is installed secondary ion and secondaryelectron detector 20 so that the secondary ion and secondary electrongenerated by a workpiece can be detected. Furthermore, electron shawerradiating member 21 is installed above secondary ion and secondaryelectron detector 20 to prevent a workpiece from being electrified.

The inside of the processing system set forth above has a structurekeeping itself under vacuum by vacuum pump 22 shown in the drawing belowthe above-mentioned sample stand 16. Also, each of the processingsystems mentioned above is structurally controlled by each of thecontrol members 23-27 installed outside the system body so that theiroperations are controlled, and each of the control members 23-27 is alsocontrolled by controlling commuter 33 through each of the interfacemembers 28-32. Controlling commuter 33 has terminal 34, magnetic diskunit 35 to record data, and MT deck 36.

Next, the method of manufacturing mask 1 c of Embodiment 3 will bedescribed with reference to FIG. 8, FIGS. 9(a) and (b) and FIG. 10.

First, as shown in FIG. 9(a), metal layer 3 of, for example, 500-3,000 Åis formed by sputtering or the like on the main surface of substrate 2which has been ground and cleaned. Then, mask 1 c is held by holder 15of focused ion beam system 8.

Next, an ion beam is charged from ion source 9. This ion beam isconverged by each of the above-mentioned electrodes into a beam diameterof, for example, 0.5 μm. Then, an ion beam current of approximately 1.5uA is obtained. Subsequently, this focused ion beam is irradiated onto agiven portion of metal layer 3 in accordance with the pattern data of anintegrated circuit pattern stored beforehand in a magnetic tape of MTdeck 36. Then, metal layer 3 is etched. At this juncture, theirradiation time per pixel is, for example, 3×10⁻⁶ second, and thescanning numbers are approximately 30. Thus, as shown in FIG. 9(b),metal layer 3 is patterned. The patterning of metal layer 3 may also becarried out by an electron beam exposure method or the like as in theaforementioned Embodiment 1.

After this, a given quantity of ion beam is irradiated onto thealignment mark provided on mask 1 c, which is not shown in the drawing,so as to detect a generated secondary electron by secondary ionsecondary electron detector 20, and the position coordinates arecomputed in accordance with the detection data.

Then, based on the position coordinates of the alignment mark thusworked out, sample stand 16 is moved so that the ion beam can beirradiated onto the location where phase shifting groove 7 a is formed.

Next, in accordance with the pattern data of phase shifting groove 7 a,the ion beam is irradiated onto substrate 2, which has been exposed bythe pattern formation of metal layer 3, along the contour of metal layerto form phase shifting groove 7 a (FIG. 6). At this juncture, the depth,width and others of phase shifting groove 7 a can be defined by thefocused ion beam accurately with ease.

The pattern data of phase shifting groove 7 a is prepared by a logicarithmetic operation on the pattern data of light shield region A (ortransmission region B) and the pattern data obtainable by magnifying ordemagnifying the pattern data of light shield region A (or transmissionregion B).

For example, as shown in FIG. 10, the pattern data of an integratedcircuit is first prepared through the process of LSI circuit design(Step 101 a), CAD design data (101 b), and Boolean OR (101 c) and thenthe data is produced by the sizing process (102) for the patterned datahaving the pattern width of light shield region A which has beenthickened only by a given dimension. At the same time, the data forpattern data of transmission region B are prepared in the process ofreverse tone (103) by reversing the positive pattern data of anintegrated circuit pattern into the negative one. Then, the pattern dataof phase shifting groove 7 a are automatically prepared (105) byexecuting AND of these pattern data (104).

Next, after phase shifting groove 7 a has been formed, the bottom faceof phase shifting groove 7 a formed on mask 1 c is flattened by dryetching with a gas plasma of, for example, Freon (CF₄) or the like. Withthis flattening of the bottom face of phase shifting groove 7 a, theoperativity of phase of the light being transmitted through this groovecan be improved. In this respect, when the dry etching treatment iscarried out, a gas of Freon or the like is supplied for 20 scc/min tothe inside of a treatment chamber of plasma dry etching, the pressure ofwhich is reduced, for example, to 0.1 Torr.

In this way, mask 1 c shown in FIGS. 6 and 7 is manufactured.

Next, the function of mask 1 c of Embodiment 3 will be described withreference to FIGS. 11(a)-(d).

Now, when the original of a given integrated circuit pattern on mask 1 cshown in FIG. 11(a) is transferred by a method of demagnifyingprojection exposure or the like, a phase contrast of 180° is generated(FIGS. 11(b) and (c)) between the light being transmitted through phaseshifting groove 7 a and the one through the normal transmission region Bin each of transmission regions B of mask 1 c. Here, the lightstransmitted through the same transmission region B having a reversephase respectively weaken each other at the boundary area oftransmission region B and light shield region A because phase shiftinggroove 7 a is arranged around transmission region B on mask 1 c. As aresult, the bleeding of the contour of the projected image on a wafercan be reduced, and the contrast of a projected image and depth of focuscan be improved remarkably (FIG. 11(d)). Also, since the light intensityis the square of the light amplitude, the waveform in the negative sideof the light amplitude on a wafer will be reversed into the positiveside as shown in FIG. 11(d).

Thus, the following effects can be attained according to Embodiment 3:

(1). While lights are being transmitted through each of the transmissionregions B at the time of exposure, a phase contrast of 180° is generatedbetween the light transmitted through phase shifting groove 7 a and theone through the normal transmission region B. These lights thustransmitted weaken each other at the boundary area of light shieldregion A and transmission region B, making it possible to reduce thebleeding of contour of the image projected on a wafer. As a result, thecontrast of the projected image is considerably improved so that theresolution and depth of focus can be improved remarkably.

(2). Through (1) mentioned above, more tolerance for exposure can beallowed.

(3). Since a phase contrast can be generated within one transmissionregion B, the arrangement of phase shifting groove 7 a is notrestricted. Also, the arrangement of phase shifting groove 7 a is notdifficult no matter how narrow the pattern width is in light shieldregion A. Consequently, the pattern transfer accuracy will never belowered locally even when a pattern formed on mask 1 c is highlycomplicated and fine like the pattern of an integrated circuit so thatthe pattern transfer accuracy of the entire pattern formed on mask 1 ccan be improved remarkably.

(4). The pattern data of phase shifting groove 7 a can be obtainedautomatically based on the pattern data of light shield region A ortransmission region B, making it possible to prepare the pattern data ofphase shifting groove 7 a with ease and reduce its preparation timeconsiderably.

(5). Since a means for shifting the phase of light can be the phaseshifting groove 7 a instead of the transparent film as in theaforementioned Embodiments 1 and 2, the process of forming a transparentfilm is no longer needed when mask 1 c is manufactured.

(6). In addition to the above-mentioned (4) and (5), the phase shiftinggroove 7 a can also be formed when the patterning of metal layer 3 iscarried out by focused ion beam, so that the mask manufacturing processcan be simplified as compared with the one using a transparent film asthe means of shifting phase, and its manufacturing time can be reducedconsiderably.

(7). Since the manufacturing process of phase shifting mask can besimplified, exterior defects, adhesion of foreign materials, or anyothers are prevented effectively as compared with the mask usingtransparent film as means for shifting phase of light.

(8). In case of using phase shifting groove 7 a, there is nodeterioration of, for example, the quality of film, transmission rate,or adhesiveness to substrate 2 due to irradiation light or exposurelight after the mask manufactured as in the case of using a transparentfilm for phase shifting.

(9). Through (8) mentioned above, the life of a mask can be prolonged ascompared with the mask using the transparent film as the means forshifting the phase of light.

(10). Through (8) mentioned above, the accuracy of phase operation oflight can be maintained longer than the mask using the transparent filmas the means for shifting the phase of light.

(11). In the case of phase shifting groove 7 a, there is no need ofconsideration for any deterioration of the quality of film and others asin the case of using a transparent film as the means for shifting thephase of light. Consequently, such treatment as ozone sulfuric acidcleaning at a high-temperature or high pressure water scribble cleaningor others can be conducted for mask 1 c.

(12). Through (11) mentioned above, a removal treatment of foreignmaterials can be conducted better than the mask using a transparent filmas the means for shifting the phase of light.

Embodiment 4

FIG. 12 is a sectional view of the principal part of another maskembodying the present invention, FIG. 13(a) is a sectional view of themask shown in FIG. 12 in a state of exposure, and FIGS. 13(b)-(d) arediagrams representing the amplitude and intensity of the light beingtransmitted through the transmission region of the mask shown in FIG.12.

In mask 1 d of Embodiment 4 shown in FIG. 12, phase shifting groove 7 bis arranged in the vicinity of the central part of transmission regionB.

In this case, too, phase shifting groove 7 b is formed on substrate 2 insuch a manner that its depth d will satisfy the relation ofd=λ/[2(n₂−1)] so as to generate as shown in FIGS. 13(a)-(d) the phasecontrast of 180° between the light transmitted through phase shiftinggroove 7 b and the one through the normal transmission region B in eachof transmission regions B, B of mask 1 d (FIGS. 13(b) and (c)). Theselights thus transmitted will weaken each other at the boundary area oftransmission region B and adjacent light shield region A, A so that thebleeding of contour of the image projected on a wafer can be reduced. Asa result, the contrast of a projected image can be considerablyimproved, making it possible to improve the resolution and depth offocus remarkably (FIG. 13(d)).

Also, in this case, the pattern data of phase shifting groove 7 b canautomatically prepared by thinning by a given dimension, the width of apattern of transmission region B obtainable by reversing the positivepattern data of, for example, an integrated circuit pattern to thenegative one. According to Embodiment 4, therefore, the same effect asin the aforementioned Embodiment can be attained.

Embodiment 5

FIG. 14 is a sectional view of the principal part of still another maskembodying the present invention, FIG. 15 is a top plan view of theprincipal part of the mask shown in FIG. 14, FIG. 16 is a top plan viewof the principal part of a mask showing an example of pattern data for agroove and sub-transmission region, FIG. 17 is a flow chart representingthe procedures through which the pattern data for the groove andsub-transmission region shown in FIG. 16 are prepared, FIGS. 18(a)-(i)are illustrations showing the shapes of the pattern in the course offorming the pattern for the groove and sub-transmission in FIG. 16, FIG.19(a) is a sectional view of the mask shown in FIGS. 14 and 15 in astate of exposure, and FIGS. 19(b)-(d) are diagrams representing theamplitude and intensity of the light being transmitted through thetransmission region of the mask shown in FIGS. 14 and 15.

The mask 1 e of Embodiment 3 will subsequently be described withreference to FIGS. 14 and 15.

In mask 1 e of Embodiment 5, a plurality of grooves 37 which extendrespectively from the top surface of metal layer 3 to the main surfaceof substrate 2 are arranged on the metal layer comprising light shieldregion A.

Groove 37 is, as shown in FIG. 15, is arranged in parallel alone eachside of transmission region B in such manner that surrounds each ofrectangular transmission regions B, B. The width of groove 37 is, forexample, approximately 0.5 μm.

Above groove 37, there is provided transparent film 4 c made of indiumoxide (InO_(x)) or the like having, for example, a refractive index of1.5.

With transparent film 4 c, mask 1 e is so constructed that it generatesa phase contrast between the light transmitted through transparent film4 c and groove 37 and the one through transmission region B at the timeof exposure.

Given the thickness of transparent film 4 c measured from the mainsurface of substrate 2 is X₂, transparent film 4 c is formed, as in theaforementioned Embodiment to satisfy the relation of X₂=λ/[2(n₁−1)].This relation is maintained in order to generate a phase contrast of180° between the phase of light transmitted through transparent film 4 cand groove 37 and the phase of one through transmission region B in thelights irradiated onto mask 1 c at the time of exposure. For example, inirradiated at case where the wavelength of light λ irradiated at thetime of exposure is 0.365 μm (i line), the thickness X₂ of transparentfilm 4 c measured from the main surface of substrate 2 can beapproximately 0.37 μm.

Furthermore, in Embodiment 5, as shown in FIG. 15 rectangularsub-transmission region C of, for example, approximately 0.5×0.5 μm indimension is arranged at each of four corners of rectangulartransmission region B. This is provided in order to prevent the fourcorners of a pattern of an integrated circuit formed at the right angleson a mask 1 e from being rounded after its development as theminiaturization of an integrated circuit pattern further advances. Inother words, sub-transmission regions C are arranged respectively ateach of the four corners in an integrated circuit pattern in order toincrease the light intensity in the vicinity of the four corners, wherethe light intensity tends to be most weakened resulting in a greaterdistortion, so that a projected image can be compensated. Also, althoughnot shown in the drawing, when, for example, groove 37 or transparentfilm 4 c is formed, an alignment mark is provided on mask 1 c to aligntheir position and that of metal layer 3.

To manufacture such a mask as mask 1 e, the subsequent procedures willbe taken, for example.

First, on the main surface of substrate 2 which has been ground, metallayer 3 of, for example, approximately 500-3,000 Å is formed bysputtering or others. Subsequently, this substrate is held on holder 15of focused ion beam system 8 described in the aforementioned Embodiment3.

Next, metal layer 3 on the main surface of substrate 2 is patterned byfocused ion beam in accordance with the data of an integrated circuitpattern stored beforehand in the magnetic tape of MT deck 36.

Likewise, after this, groove 37 is formed on metal layer 3 byirradiating the focused ion beam onto metal layer 3 on the main surfaceof substrate 2 in accordance with the pattern data of groove 37 andsub-transmission region C stored beforehand in the magnetic tape of MTdeck 36.

The pattern data of groove 37 and sub-transmission region C, as will bedescribed later, can automatically be prepared by providing anarrangement rule against rectangular transmission region B.

Then, the pattern data of transparent film 4 c is prepared in accordancewith the pattern data of an integrated circuit pattern and those ofgroove 37 and sub-transmission region C. Based on this, transparent film4 c is formed on mask 1 c in the same manner as in the aforementionedEmbodiment 1.

Here, the method of preparing the pattern data of groove 37 andsub-transmission region C formed on an integrated circuit pattern shownin FIG. 16 as an example will be described along the flow chart shown in17 with reference to FIGS. 18(a)-(i). To facilitate examining thedrawings, however, transparent film 4 c is not shown in FIG. 16. Also,crosshatchings in FIGS. 18(a)-(i) represent the patterns produced ineach process respectively.

First, the data of pattern 38 in transmission region B as shown in FIG.18(a) are prepared (steps 101 a-101 c) through the processes of LSIcircuit design, CAD design, and Boolean OR.

Subsequently, as shown in FIG. 18(b), pattern 39 is defined (102 a) bythickening the pattern width of transmission region B by, for example,approximately 2.0 μm through the process of sizing 1.

At the same time, through the process of sizing 2, pattern 40 isproduced (102 b) by thickening the pattern width of transmission regionB by, for example, 1.0 μm as shown in FIG. 18(c).

Next, through the process of corner clipping, the data of pattern 41having only the corners extracted from pattern 39 are prepared a shownin FIG. 18(d) (103 a). Then, through the process of reversing zones, thedata of pattern 41 thus prepared are reversed from positive to negativein order to prepare the data of pattern 42 as shown in FIG. 18(e) (104a).

Furthermore, on the other hand, through the process of reversing zones,pattern 40 produced in the above-mentioned process of sizing 2 isreversed form positive to negative, and the data or pattern 43 shown inFIG. 18(f) are prepared (103 b).

Then, the data of pattern 44 for groove 37 as shown in FIG. 18(g) areprepared (105 a and 106 a) by executing AND of the data of patterns 39,42, and 43 shown respectively in FIGS. 18(b), (e) and (f).

Meanwhile, the data of pattern 45 shown in FIG. 18(h) are prepared (104b) by executing AND of the data of pattern 40 shown in FIG. 18(c) andthose of pattern 41 shown in FIG. 18(d).

Subsequently, the area b of pattern 45 thus produced is judged to see ifit is smaller than ½ of the area a of pattern 41 (105 b). Through thisjudgment, those patterns, the area b of which are smaller than ½ of thearea a are selected, and the data of pattern 46 of sub-transmissionregion C shown in FIG. 18(i) are prepared (106 b). The reason why thearea of pattern 45 is compared with a given value is thatsub-transmission C region should necessarily be added only to the cornersection having

shape of pattern 38 in transmission region B.

Next, the function of Embodiment 5 will be described with reference toFIGS. 19(a)-(d).

When the original of a given integrated circuit pattern on mask 1 cshown in FIG. 19(a) is transferred onto a wafer by the method ofdemagnifying exposure or the like, a phase contrast of 180° is generatedbetween the light transmitted through transparent film 4 c and groove 37and the one through transmission region B (FIGS. 19(b) and (c)) in eachof transmission regions B in mask 1 c.

Here, the light transmitted through transparent film 4 c and groove 37and the one through transmission region B weaken each other at the endtransmission region B. Therefore, the bleeding of contour of the imageprojected on a wafer can be reduced to improve the contrast of theprojected image considerably, so that the resolution and depth of focuscan be improved remarkably. Now, since the light intensity is the squareof the light amplitude, the waveform in the negative side of lightamplitude on a wafer is reversed to the positive side as shown in FIG.19(d).

In this way, the following effects can be attained according toEmbodiment 5:

(1). While lights are being irradiated onto mask 1 e at the time ofexposure, a phase contrast of 180° is generated between the lighttransmitted through transparent film 4 c and groove 37 and the onethrough transmission region B. These lights are made to weakenthemselves each other at the end portion of light shield region A,making it possible to reduce the bleeding of contour of the imageprojected on a wafer. As a result, the contrast of the projected imagecan be improved considerably so that the resolution and depth of focuscan be improved remarkably.

(2). Through (1) mentioned above, more tolerance for exposure can beallowed.

(3). Through (1) mentioned above, the accuracy of pattern transfer canbe improved.

(4). The accuracy of pattern transfer can be improved more by providingsub-transmission region C at each of four corners of transmission regionB because its provision allows the light intensity of the projectedimage there to be further intensified.

(5). The time required for manufacturing a phase shifting mask canconsiderably be reduced as compared with the previous one byautomatically producing the patterns of groove 37 and transparent film 4c.

Embodiment 6

FIG. 20 is a sectional view of the principal part of still another maskembodying the present invention, FIG. 21 is a top plan view of theprincipal part of the mask, FIG. 22(a) is a sectional view of the maskshown in FIGS. 20 and 21 in a state of exposure, and FIGS. 22(b)-(d) arediagrams representing the amplitude and intensity of the light beingtransmitted through the transmission region.

Mask 1 f of Embodiment 6 will subsequently be described with referenceto FIGS. 20 and 21.

In mask 1 f of Embodiment 6, phase shifting groove 7 c is formed onsubstrate 2 located below groove 37 instead of transparent film 4 c ofthe aforementioned Embodiment 5 as means for generating a phase contrastbetween the light transmitted through groove 37 and the one throughtransmission region B.

Given the depth of phase shifting groove 7 c is d, the refractive indexof substrate 2 is n₂, and the wavelength of exposure light is λ, thephase shifting groove 7 c is formed to maintain the relation ofd=λ/[2(n₂−1)] as in the aforementioned Embodiment 3.

For example, in case where the wavelength of light λ is 0.365 μm (iline) the depth d of phase shifting groove 7 b can be approximately 0.39μm.

The bottom face of phase shifting groove 7 c is almost flattened by aplasma dry etching treatment as in the aforementioned Embodiment 3 inorder to improve the operativity of light transmitted through the endface thereof. Phase shifting groove 7 c is produced by etching substrate2 to the depth d by increasing the scanning numbers of focused ion beamwhen, for example, groove 37 is formed.

Also, in Embodiment 6 as in the aforementioned Embodiment 5, rectangularsub-transmission region C of, for example, approximately 0.5×0.5 μm isarranged at each of the four corners of rectangular transmission regionB as shown FIG. 21. Furthermore, although not shown in the drawing, thealignment mark is provided on mask 1 f in order to align its positionwith that of metal layer 3 when, for example, groove 37 orsub-transmission region C is formed.

The pattern data of groove 37 and sub-transmission region C are preparedin the same way as, for example, case, the pattern data of phaseshifting groove 7 c are identical to those of groove 37.

Next, the function of Embodiment 6 will be described with reference toFIGS. 22(a)-(d).

When the original of a given integrated circuit pattern on mask if shownin FIG. 22(a) is transferred onto a wafer by the method of demagnifyingexposure light or the like, a phase contrast of 180° is generatedbetween the light transmitted through groove 37 and phase shiftinggroove 7 c and the one through transmission region B (FIGS. 13(b) and(c)).

Here, the light transmitted through groove 37 and phase shifting groove7 c and the one through transmission region B in the lights irradiatedonto mask 1 f weaken each other at the end portion of light shieldregions A, A adjacent to transmission region B. As a result, thebleeding of contour of the image projected on a wafer can be reduced toimprove the contrast of the projected image considerably so that theresolution and depth of focus can be improved remarkably (FIG. 22(d)).Also, since the light intensity is the square of the light amplitude,the waveform in the negative side of the light amplitude on a wafer isreversed to the positive side as shown in FIG. 22(d).

As set forth above, in Embodiment 6, the following effects can beattained in addition to the effects (1)-(5) of the aforementionedEmbodiment 5:

(1). There is no need for the process of forming any transparent filmfor use in phase shifting, when mask 1 f is manufactured, because phaseshifting groove 7 c is employed instead of transparent film 4 c as meansfor shifting phase of light.

(2). In addition to (1) mentioned above, phase shifting groove 7 c canbe produced when groove 37 is formed on metal layer 3 by focused ionbeam, whereby the process of manufacturing the phase shifting mask canbe simplified as compared with mask 1 e as in the aforementionedEmbodiment 5, and the time required for its manufacture can be reducedremarkably.

(3). The manufacturing process of the phase shifting mask can be sosimplified that external defect, adhesion of foreign materials, or anyother causes of damage will be prevented remarkably as compared withmask 1 e of the aforementioned Embodiment 5.

(4). In case of phase shifting groove 7 c, there is no deterioration of,for example, the quality of film, the transmission rate, or adhesivenessto substrate 2 due to irradiation light or exposure light after themanufacture of the mask as in the case of a transparent film for use inphase shifting.

(5). Through (4) mentioned above, the life of the mask can be prolongedmore than the one using a transparent film as the means for shiftingphase of light.

(6). Through (4) mentioned above, the accuracy of light phase operationcan be maintained longer than with the mask using a transparent film asthe means for shifting phase of light.

(7). In case of phase shifting groove 7 c, there is no need for suchconsideration as required for deterioration of the quality of film,transmission rate, or adhesiveness, and the removal of film or others asin the case of using a transparent film as the means for shifting thephase of light. Consequently, ozone sulfuric acid cleaning or highpressure water scrabble cleaning or other treatment can be conductedagainst mask 1 f at a high-temperature.

(8). Through (7) mentioned above, the removal treatment of foreignmaterials can be conducted better than with the mask using thetransparent film as the means for shifting the phase of light.

Embodiment 7

FIG. 23 is a sectional view of the principal part of still another maskembodying the present invention.

In mask 1 g of Embodiment 7 shown in FIG. 23, phase shifting groove 7 dis produced at least on either one of a pair of transmission regions B,B having light shield region A therebetween.

The bottom face of phase shifting groove 7 d is almost flattened by aplasma dry etching treatment as in the aforementioned Embodiment 3 inorder to improve the operativity of phase of light transmitted throughit.

Embodiment 7 is applicable to the portion where an integrated circuitpattern is simply arranged as in the case of, for example, a memorycell.

Phase shifting groove 7 d is produced by etching substrate 2 to thedeath d by increasing beam scanning numbers when, for example,transmission region B is formed as in the aforementioned Embodiment 6,by etching metal layer 3 with a focused ion beam.

As set forth above, the following effects can be attained according toEmbodiment 7:

(1). At the time of exposure, the phase contrast of 180° is generatedbetween the lights each transmitted through each of transmission regionsB of the pair of transmission regions B, B having light shield region Atherebetween so that the lights each transmitted through each oftransmission regions B having shield region A therebetween can weakeneach other in light shield region A. Consequently, the resolution of animage in light shield region located between the pair of transmissionregions B can be improved, making it possible to improve the accuracy ofpattern transfer.

(2). There is no need for the process of forming transparent film in themanufacture of mask because of phase shifting groove 7 d being employedas the means of shifting the phase of light instead of the conventionaltransparent film.

(3). In addition to (2) mentioned above, the manufacturing process ofthe phase shifting mask can be simplified as compared to manufacture ofthe conventional one, and its manufacturing time can also be reducedconsiderably by producing phase shifting groove 7 d simultaneously withthe patterning of metal layer 3 by focused ion beam.

(4). Since the manufacturing process of the phase shifting mask issimplified, external defect, adhesion of foreign materials or any othercauses of damage can be prevented remarkably.

(5). In case of phase shifting groove 7 d, there is no deteriorationsof, for example, the quality of film, transmission rate, or adhesivenessby irradiation light or exposure light after the manufacture of themask, as in the case of using a transparent film for conventional phaseshifting.

(6). Through (5) mentioned above, the life of the mask having a meansfor shifting the phase of light can be prolonged more than theconvention one.

(7). Through (5) mentioned above, the accuracy for light phase operationcan be maintained longer than the conventional one.

(8). Since phase shifting groove 7 d does not require any considerationfor deteriorations of the quality of film, transmission rate oradhesiveness and the removal of film or others, ozone sulfuric acidcleaning or high pressure water scrabble cleaning or other cleaningtreatment can be conducted against mask 1 g at a high-temperature.

(9). Through (8) mentioned above, removal of foreign materials can beconducted better than with the mask using a transparent film.

As set forth above, the invention of the present inventor has beenspecifically described in accordance with embodiments. The presentinvention, however, is not limited to the aforementioned embodiments,and it is needless to say that modifications and variations are possiblewithout departing from the spirit and scope of the present invention.

For example, in the aforementioned embodiment there is described thecase where the pattern data of the phase shifting groove is prepared byexecuting AND of the pattern data obtainable by magnifying the patternof the light shield region and the pattern data of the transmissionregion. It is not limited to this case, and various modifications arepossible. For example, it can be obtained by deducting the originalpattern of the light shield region from the pattern formed by magnifyingthe pattern of the light shield region.

Also, in the aforementioned embodiments 1, 2, and 5, there is describedthe case where the transparent film employed is of indium oxide. Thecase is not limited to the application thereof. For example, silicondioxide, silicon nitride, magnesium fluoride or polymethyl methacrylateor the like can be applied.

The descriptions set forth above have been made chiefly as to theapplication of the invention by the present inventor to the mask used inthe process of manufacturing semiconductor integrated circuit devices,which is the industrial field defining the background of the invention.The present invention, however, is not limited to such an applicationonly. It may be applicable to various technical fields where a transferof a given pattern to a given substrate is required.

The typical effects obtainable by the invention disclosed in the presentapplication will subsequently be described briefly.

According to the first invention, the light transmitted through thetransparent film or phase shifting groove and the light transmittedthrough the portion where these are not provided interfere with eachother at the boundary area of transmission and light shield regions soas to weaken themselves in each of transmission regions at the time ofexposure. Thus, the bleeding of contour of an image projected on a wafercan be reduced so that the contrast of the projected image is improvedconsiderably resulting in a remarkable improvement of the resolution anddepth of focus. Especially, in this case, the phase contrast isgenerated within the lights being transmitted through one transmissionregion. Therefore, there is no restriction imposed upon the arrangementof transparent film no matter how complicated the pattern is on themask. Also, the arrangement of transparent film can be made withoutdifficulty no matter how narrow the pattern width is in the transmissionregion. As a result, the accuracy of pattern transfer will not belowered locally, making it possible to improve remarkably the transferaccuracy of the entire pattern formed on the mask.

According to the second invention, the manufacturing time of the maskhaving a means for shifting the phase of light can be reducedconsiderably because there is no need for preparing specially anypattern data of transparent film or phase shifting groove.

According to the third invention, the light transmitted through thetransmission region and the light transmitted through the groove andphase shifting groove interfere with each other to weaken themselves atthe end portion of the transmission region so that the bleeding ofcontour of an image projected on a wafer can be reduced, and thecontrast of the projected image will be improved considerably, making itpossible to improve the resolution and depth of focus remarkably. As aresult, the accuracy of pattern transfer can be improved.

According to the fourth invention, the light intensity at the corners ofthe transmission region is increased by arranging sub-transmissionregions at the corners of the transmission region so that not only theresolution of the projected image at each side but also the resolutionof the corners thereof can be improved.

1. A semiconductor integrated circuit device fabrication method,comprising the steps of: disposing a semiconductor substrate having aphotoresist film on a position in an optical reducing projectionexposure system; providing a mask comprising: (a) a phase shifting filmcovering region, over a flat major surface of a transparent masksubstrate; (b) an opening region, in the phase shifting film coveringregion, there being no phase shifting film in the opening region; and(c) a shifter edge region of the phase shifting film covering region,which shifter edge region borders on and is adjacent to the openingregion, the shifter edge region having a phase shifting film over theflat major surface of the transparent mask substrate; mounting the maskto the optical reducing projection exposure system such that a frontsurface of the mask with the phase shifting film formed thereon facesdown; and transferring a pattern formed on the mask onto thesemiconductor substrate having the photoresist film with an exposurelight flux, said exposure light flux being at least partially coherentin an ultraviolet domain and transmitting the mask from the back surfaceof the mask without the phase shifting film to the front surface of themask with the phase shifting film, wherein the exposure light fluxtransmits through the shifter edge region contacted with the border ofthe opening region and a phase of the transmitted exposure light fluxtransmitted through the shifter edge region is inverted with respect tothat of the transmitted exposure light flux transmitted through theopening region, due to only said transmission through the phase shiftingfilm, and whereby resolution is improved due to destructive interferencebetween exposure light fluxes transmitted through the opening region andthe shifter edge region.
 2. A semiconductor integrated circuit devicefabrication method according to claim 1, wherein the mask substrate andphase shifting film are made of different materials from each other. 3.A semiconductor integrated circuit device fabrication method accordingto claim 1, wherein the exposure light flux transmits through the wholeshifter edge region.
 4. A semiconductor integrated circuit devicefabrication method, comprising the steps of: disposing a semiconductorsubstrate having a photoresist film on a position in an optical reducingprojection exposure system; providing a mask comprising: (a) a phaseshifting film covering region, over a flat major surface of atransparent mask substrate; (b) an opening region, in the phase shiftingfilm covering region, there being no phase shifting film in the openingregion; and (c) a shifter edge region of the phase shifting filmcovering region, which shifter edge region borders on and is adjacent tothe opening region, the shifter edge region having a phase shifting filmover the flat major surface of the transparent mask substrate; mountingthe mask to the optical reducing projection exposure system such that afront surface of the mask with the phase shifting film formed thereonfaces down; transferring the pattern formed on the mask onto thesemiconductor substrate having the photoresist film with an exposurelight flux, said exposure light flux being at least partially coherentin an ultraviolet domain and transmitting through the mask from the backsurface of the mask without the phase shifting film to the front surfaceof the mask with the phase shifting film; and moving the semiconductorsubstrate step by step so that the pattern formed on the mask can betransferred onto the surface of the semiconductor substrate, wherein theexposure light flux transmits through the shifter edge region contactedwith the border of the opening region and a phase of the transmittedexposure light flux transmitted through the shifter edge region isinverted with respect to that of the transmitted exposure light fluxtransmitted through the opening region, due to only said transmissionthrough the phase shifting film, and whereby resolution is improved dueto destructive interference between exposure light fluxes transmittedthrough the opening region and the shifter edge region.
 5. Asemiconductor integrated circuit device fabrication method according toclaim 4, wherein the mask substrate and phase shifting film are made ofdifferent materials from each other.
 6. A semiconductor integratedcircuit device fabrication method according to claim 4, wherein theexposure light flux transmits through the whole shifter edge region. 7.A semiconductor integrated circuit device fabrication method, comprisingthe steps of: disposing a semiconductor substrate having a photoresistfilm on a position in an optical reducing projection exposure system;providing a mask comprising: (a) a phase shifting film covering region,over a major surface of a transparent mask substrate without any phaseshifting grooves; (b) an opening region, in the phase shifting filmcovering region, there being no phase shifting film in the openingregion; and (c) a shifter edge region of the phase shifting filmcovering region, which shifter edge region borders on and is adjacent tothe opening region, the shifter edge region having a phase shifting filmover the major surface of the transparent mask substrate; mounting themask to the optical reducing projection exposure system; andtransferring a pattern formed on a mask onto the semiconductor substratehaving a photoresist film with an exposure light flux, said exposurelight flux being at least partially coherent in an ultraviolet domainand transmitting through the mask from the back surface of the maskwithout the phase shifting film to the front surface of the mask withthe phase shifting film, wherein the exposure light flux transmitsthrough the shifter edge region contacted with the border of the openingregion and a phase of the transmitted exposure light flux transmittedthrough the shifter edge region is inverted with respect to that of thetransmitted exposure light flux transmitted through the opening region,due to only said transmission through the phase shifting film, andwhereby resolution is improved due to destructive interference betweenexposure light fluxes transmitted through the opening region and theshifter edge region.
 8. A semiconductor integrated circuit devicefabrication method according to claim 7, wherein the mask substrate andphase shifting film are made of different materials from each other. 9.A semiconductor integrated circuit device fabrication method accordingto claim 7, wherein the exposure light flux transmits through the wholeshifter edge region.
 10. A semiconductor integrated circuit devicefabrication method according to claim 7, wherein a metal layer made ofchrome or the like is not formed in the shifter edge region contactedwith the border of the opening region.
 11. A semiconductor integratedcircuit device fabrication method, comprising the steps of: disposing asemiconductor substrate having a photoresist film on a position in anoptical reducing projection exposure system; providing a maskcomprising; (a) a phase shifting film covering region, over a majorsurface of a transparent mask substrate without any phase shiftinggrooves; (b) an opening region, in the phase shifting film coveringregion, there being no phase shifting film in the opening region; and(c) a shifter edge region of the phase shifting film covering region,which shifter edge region borders on and is adjacent to the openingregion, the shifter edge region having a phase shifting film over themajor surface of the transparent mask substrate; mounting the mask tothe optical reducing projection exposure system; and transferring thepattern formed on the mask onto the semiconductor substrate having thephotoresist film with an exposure light flux, said exposure light fluxbeing at least partially coherent in an ultraviolet domain andtransmitting through the mask from the back surface of the mask withoutthe phase shifting film to the front surface of the mask with the phaseshifting film; and moving the semiconductor substrate step by step sothat the pattern formed on the mask can be transferred onto the surfaceof the semiconductor substrate, wherein the exposure light fluxtransmits through the shifter edge region contacted with the border ofthe opening region and a phase of the transmitted exposure light fluxtransmitted through the shifter edge region is inverted with respect tothat of the transmitted exposure light flux transmitted through theopening region, due to only said transmission through the phase shiftingfilm, and whereby resolution is improved due to destructive interferencebetween exposure light fluxes transmitted through the opening region andthe shifter edge region.
 12. A semiconductor integrated circuit devicefabrication method according to claim 11, wherein the mask substrate andphase shifting film are made of different materials from each other. 13.A semiconductor integrated circuit device fabrication method accordingto claim 11, wherein the exposure light flux transmits through the wholeshifter edge region.
 14. A semiconductor integrated circuit devicefabrication method according to claim 11, wherein a metal layer made ofchrome or the like is not formed in the shifter edge region contactedwith the border of the opening region.